Goldstone Radar Images of 2014 BR57

Sequence of images with a resolution of 3.75 meters x 0.06 Hz. Time delay (range)
increases down and Doppler frequency increases to the right, so the rotation is
counterclockwise. Each image is a weighted sum of 15 individual transmit-receive cycles.
The images were obtained during an interval of 4.2 hours
on February 18 when the asteroid was 0.018 AU (7 lunar dsitances) from Earth.
The images indicate that 2014 BR57 is a rounded object and suggest that it's roughly
80 meters in diameter. Radar-bright spots appear in two locations and persist over a
range of rotation phases. The spots appear in frames 5, 6, 7 at the trailing edge of
the echo and in frames 11, 12, and 13 near the two o'clock position.
The spots are more conspicuous in the movie (a link is provided below).
The images suggest that the rotation period is a few hours.
Radar astrometry obtained on Feb. 18 permits reliable orbit estimation for
261 years and has prevented this object from being lost. The encounter in 2014 was
the closest for the forseeable future.
Although there have been problems recently with one of the klystrons, we were
fortunate with these observations that both klystrons were operational and that
we were able to transmit 440 kW.